Need help with vacuum leak

[detch]

Need help with a vacuum leak, when I turn on the car but not start it the pump keep running, when I pull the one hose off the driver side of the plenum and plug it the pump stops. I tried to pull a vacuum on the plenum's connector but it won't hold a vacuum. any ideas?

thanks
Mike

[LGAFF]

Are you testing vac off the P/S that is running from near the coolant overflow into the plenum? You should be able to hold vac if you plug your vac tester into the line running to the plenum. It should hold with slow leakdown at least.

If not there is a good chance you have a leak under the plenum.

LGAFF
92 ZR1
#234

[tomtom72]

If you can't hold any vacuum on the plenum side of the line you could see if you can find a vacuum check valve that fits the connector. Plug it into the line going under the plenum and re-do the vac test. If you hold vacuum upon the retest then you have solved the issue. There is a vacuum check valve in the hose network under the plenum that could have given up the ghost.

If that new check valve does not help, then the 2* control solenoid, reserve storage tank, maybe even the actuators or a leak in the actual hose are likely suspects. Unless you are setting a DTC61, I would say that the actuators are okay. To get an eyeball on what is under the plenum use this link.

http://www.corvetteactioncenter.com/...ad.php?t=14272

some great stuff that gives a great explaination.

[detch]

the vacuum is from the electric vacuum pump in the fron passanger side of the car. I check the hose from the check valve to the pump and they are fine, I wanted to check the connections on the outside of the plenum, when I remove the hose from the manifold vacuum (6e3-c2-6 fig c2-7 block #2) in service manual and pluged it, the moter stops, so I think the leak is between this connector on the plenum and where ever it goes, I just don't know where it goes.
I not talking from the connector to the check valve under the plenum I talking the other way from the connector on the plenum into the plenum



Mike

Originally Posted by detch

the vacuum is from the electric vacuum pump in the fron passanger side of the car. I check the hose from the check valve to the pump and they are fine, I wanted to check the connections on the outside of the plenum, when I remove the hose from the manifold vacuum (6e3-c2-6 fig c2-7 block #2) in service manual and pluged it, the moter stops, so I think the leak is between this connector on the plenum and where ever it goes, I just don't know where it goes.
I not talking from the connector to the check valve under the plenum I talking the other way from the connector on the plenum into the plenum



Mike

From the driver side port, the line goes into a check valve, then from there goes directly into a "T" port on the line. The two other sections of the "T", 1 goes to the vacuum pump, the other goes to the vacuum reservoir.

[rhipsher]

Check valves don't give up the ghost. They just get dirty and clogged. There are actually two check valves under the plenum. One in the front and one in the back. Easy way to check it is to unhook it and block the single perpendicullar outlet with your finger and blow through the other two ends. It should only allow air flow in one direction. If you are able to blow air through in both directions then its got dirt in it. All there is is a little bee bee ball inside of it. Just take some carburator cleaner and spray it in all the outlets. Then blow it dry. Then take some WD40 and also spray it in all the outlets. Check valve will be as good as new. But hell what do I know. Also when it comes to secondary port throttle failure be suspicious of the secondary vacume solenoid. It has a little cheesy air filter on it and over the years will evetually get old and turn to dust allowing contaminents to get sucked up into it and cause it to fail giving you that "Run out of breath at 4000rpm''s old man caugh under hard acceleration (SES light)error code 61 BS".

[detch]

Well, I puilled the plenum and cheched the connections and found a loose one connection at the T. I put it all back together and the vac pump keeps running.
I pulled the the connector off at the plenum on the driver side and plug it and the vacuume pump stopped. I put it back on plenum and it started running again.
any ideas?
Will this prevent the secondaries from operating (no full power)?
What would happen if I just plugged the connector and did not connect it to the connector on the plenum?

thanks
Mike

[tccrab]

Originally Posted by detch

Well, I puilled the plenum and cheched the connections and found a loose one connection at the T. I put it all back together and the vac pump keeps running.
I pulled the the connector off at the plenum on the driver side and plug it and the vacuume pump stopped. I put it back on plenum and it started running again.
any ideas?
Will this prevent the secondaries from operating (no full power)?
What would happen if I just plugged the connector and did not connect it to the connector on the plenum?

thanks
Mike

Mike:

A bad check valve?
Hmmm..
Gonna go dig out my FSM...

Your '95 is a little different under the plenum than my '90, but they work the same. There is a check valve (item #15 pg 6A2A-33 LT5 Service Manual Supplement) located inline with that hose which is connected to the plenum. If that check valve is breached, it will allow the vacuum pump to suck air past the valve and cause the vacuum pump to run continuously.
If I read the diagram correctly, the check valve allows the vacuum pump to pull a vacuum on the secondary system until the engine starts producing suitable vacuum. When the magic pressure is reached, the check valve opens and the ECM directs the vacuum pump to stop.

I'm just guessing, but if you were to plug this line it's possible that the secondaries might not have enough vacuum to:
A: open the secondaries completely, or;
B: hold them open for any appreciable lenght of time.

TomC
'Crabs"

[detch]

Bad check valve was it, all fixed.
thanks all for the help

Mike

!

[tomtom72]

Good deal Mike! Now go play with the toy!